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Shawn Vestal: The miracle and wonderment of the ice crystal

February 13, 2019

Editor’s note: This column was written in consultation with Von Walden, an atmospheric researcher with the Department of Civil and Environment Engineering at Washington State University. Walden’s research includes studying atmospheric ice crystals at the South Pole Station in Antarctica.

It begins invisibly, in the air above the sea.

Molecules of water vapor, trillions upon trillions, escape from the ocean, rise and join water vapor from other sources to condense in tiny droplets suspended in a gray mass thousands of feet above the earth.

Thus they travel from ocean to air, evolving from water to vapor to water.

When the temperature freezes and the humidity is high, the water droplets in the cloud begin to form crystals. They attach to tiny particles in the atmosphere – bits of ash, of dust, of minerals, of metals, far too minuscule to see with the eye. Like the grain of sand in an oyster, like the seed that produces the tree, each particle becomes the catalyst for one of nature’s routine, numberless miracles: an ice crystal.

The smallest are very small indeed, perhaps the width of a human hair. The larger ones might be the width of a penny.

The cloud – that zeppelin of suspended water droplets and ice crystals – transforms, molecule by molecule, trillion by trillion, into a sparkling airborne sea, comprised of tiny crystal palaces scattering light.

The crystals are almost all hexagonal – six-sided – but they appear in a range of shapes and configurations.

Stellar dendrites and fern-like dendrites.

Plates of ice and needles of ice. Columns of ice and pyramids of ice.

Sectored plates and bullet rosettes.

It is often said no two of them are the same. It is also often said that given the vast variety of shapes they assume – coupled with the uncountable number of ice crystals that have fallen and are falling and will fall upon the earth – that it is impossible to make such a claim.

That we should be humble about the limits of the knowable.

These crystals, this crystalline sea, is not just frozen water; it is nothing so mundane as that. Frozen water that falls to earth is sleet. Frozen water that falls to earth is freezing rain. Snow crystals are a finer alchemy. They are delicate and intricate and beautiful, the product of a true metamorphosis.

As the crystals form and grow upon the tiny particles inside the cloud, building upon the lattice-like structure of the water molecules, they gain weight and mass. When they become heavy enough – though still so very light – they fall from the cloud toward the earth. The shapes these crystals will assume are affected by the atmosphere – temperature, humidity and the path the crystals travel toward the ground.

This metamorphosis occurs all over the planet’s upper atmosphere, and not just in wintry places. Ice crystals are nearly always present in the atmosphere above the Antarctic Plateau, but they can also form over, say, Hawaii, way up where the air is thin and cold. There, though, the entire cycle may occur well above the earth’s surface – the falling ice crystals will melt back into water, or even vaporize, when they reach the warmer atmosphere below.

But when it’s cold down below – when it’s at or below freezing for days on end – the crystals fall, merging and clumping, taking on new shapes and characteristics as they pass through atmospheric layers.

They might fall lightly, sparingly, as they did during much of the day on Sunday here – such sparse, dry descents that it seems to have to have stopped completely. Or they might fall heavily, gathering thickly on cheeks and eyebrows, swirling densely to the curvature of the wind, as it did Sunday night and Monday night.

You can catch them in your hand, these tiny crystals, and watch them as they melt and die, five of them, then 10, then 30, then 40, before your hand gets so cold you stop counting.

En route and on earth, the crystals are buffeted and battered by the wind and other elements. They crash into each other. Their delicate structures break and are rounded, sometimes becoming spherical and clumping into larger particles.

They gather thickly everywhere, these trillions and trillions. They layer the earth. They fill driveways and sidewalks and roads. They perch delicately along tree limbs and power lines, like reverse shadows, and tuck into crannies and corners, cap the world with crystalline mounds. At night as they fall, they light up the sky, creating a lilac glow.

It is the world at its most mysterious and magical, an expression of the way nature’s tiniest forms work on scales of such vastness that our minds cannot truly accommodate the wonder. We drive, we shovel, we sled, we ski, we complain, we exult – all without considering the marvel around us.

The crystals are evanescent, mutable, changing as the world itself is continually changing. Even now, these crystals that bury us – these crystals that came here having metamorphosed from water to vapor to water to crystals – even now they are changing, becoming denser as the crystals break and lock together. The temperatures will rise and fall, altering them further, pushing their fragile forms back toward water, back toward vapor.

The crystals will transform again and travel. They will melt and enter the earth, melt and enter streams and rivers, which will flow toward a larger river, which will flow toward another, which will flow and flow, once more as it has for millennia, to the sea.

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